Modeling, Control and Power Management Strategy of a Grid connected Hybrid Energy System (original) (raw)

This paper presents the detailed modeling of various components of a grid connected hybrid energy system (HES) consisting of a photovoltaic (PV) system, a solid oxide fuel cell (SOFC), an electrolyzer and a hydrogen storage tank with a power flow controller. Also, a valve controlled by the proposed controller decides how much amount of fuel is consumed by fuel cell according to the load demand. In this paper fuel cell is used instead of battery bank because fuel cell is free from pollution. The control and power management strategies are also developed. When the PV power is sufficient then it can fulfill the load demand as well as feeds the extra power to the electrolyzer. By using the electrolyzer, the hydrogen is generated from the water and stored in storage tank and this hydrogen act as a fuel to SOFC. If the availability of the power from the PV system cannot fulfill the load demand, then the fuel cell fulfills the required load demand. The SOFC takes required amount of hydrogen as fuel, which is controlled by the PID controller through a valve. Effectiveness of this technology is verified by the help of computer simulations in MATLAB/SIMULINK environment under various loading conditions and promising results are obtained. 1. INTRODUCTION Due to the considerations of environment condition, applications of renewable energy sources (RESs) are more promising; that makes environment pollution free. Also, their availability is cost free and continuous [1], [2]. Numerous RESs consist of photovoltaic system (PV), wind turbine system (WT) and micro-turbines, etc. which are considered as components of hybrid energy systems in the literature and also demonstrate applications of micro-grid [3], [4]. Due to the various seasonal and bad weather conditions such as temperature, wind speed, solar radiation and also geographical conditions, these structures are not worked properly. So, the solutions must be needed and find out. Hence, energy storage systems (ESSs) are suitable for the solution of the mitigation of wind effects, solar radiation fluctuations and also ESSs uphold the power and energy balance. Power quality also improves due to ESSs. Due to the fast variations of power, ESSs must contain a high power density as well as high energy density. So, it is required to keep more than one storage system for a hybrid energy storage system (HESS) [5]-[7]. The ESSs and battery banks (BBs) are efficiently used in hybrid energy systems (HESs). But, lifetime of batteries decreases due to the charging and discharging cycles [8], [9]. A secondary energy sources is required to enhance the supply energy reliability of HESs. Hence, a fuel cell (FC) is required to combine with the electrolyzer by giving a continuous supply to the load [10], [11]. The strategies of energy management consist of combination of PV, WT and FC comprising with electrolyzer as well as battery storage. These are most effective practice for quality of higher